>>i wonder if it is the words themselves that make these people upset, or just the emotions behind them?

An argument for it being the words themselves would be the high percentage of swear words being related to what people hold sacred, such as deity, acts of love, anatomy, and others.

An argument for it being the emotions behind the words would be the fact that few of those using these "sacred" words are trying to be literally blasphemous, but are instead using it for shock value or emphasis.